There are ever increasing applications which require that video data, including high definition (HD) video, be transmitted over wireless paths. For instance, HD video may be transmitted over wireless digital visual interface (DVI) paths from a source to a player.
Regardless of how the data is transmitted, the use of two clocks may be required when the video clock rate is different from a reference clock rate. The video clock refers to the rate at which the video data is encoded at a source and then decoded at a display, while and the reference clock refers to the clock rate of the transmission system itself. The difficulty arises from the fact that the source of video on the transmitter side and the video player on the receiver side must use the same video clock for encoding/decoding. Similarly, the transmitter and receiver of the communication system must use the same reference clock.
While it is well known how the transmitter and receiver in a communication system are able to maintain the reference clock, it is a more difficult task to ensure that the video clock is properly maintained. One approach has been to simply require the video clock to be related in some predefined way to the reference clock. This way, there is no need to transmit any information about the video clock with the data, since the receiver system knows the predefined relationship the video clock has with the communication clock and can simply derive the video clock from the communication clock. Unfortunately, the requirement that the clock of the video system bear a predefined relationship to the clock of the communication system unnecessarily constrains the video system, and/or renders some video systems, which have video clocks that are established independently and arbitrarily from any communication system clock, unsuitable for transmission over the communication system.
Another approach has been to have the transmitter continuously monitor the video clock by counting the number of video clocks occurring in a given transmission time period. This “count” would then be serialized onto the video data and sent over the communication link along with the video data. This “count” would then be used by the receiver to recover the video clock. While this is an improvement to requiring a predefined relationship between the video clock and the reference clock, it requires a more complicated transmission system since the “count” has to be continuously sent to the receiver side. In addition, this approach requires that forward error correction techniques be used to ensure that the “count” is being accurately transmitted over a potentially unreliable communication link.
Thus, there is still an unsatisfied need for a system and method for using reference clock to replicate an independent video clock.